Fuel cells are devices that convert chemical energy from a fuel into electricity through a chemical reaction of positively charged hydrogen ions with air (e.g., oxygen and/or other oxidizing agents). Fuel cells, unlike batteries, require a continuous source of fuel and air to sustain the chemical reaction, generally producing electricity continuously for as long as these inputs are supplied. However, both the air and fuel need to be pure with no contaminants, otherwise there is a high risk of destroying the fuel cell. For instance, it is generally known that fuel cell stacks can experience irreversible voltage loss when exposed to certain air contaminants at high concentrations (e.g., sulfur-based air contaminants).
As an example, the Hawai'i Natural Energy Institute is building a fuel cell powered bus to be used in Hawai'i Volcanoes National Park on the Island of Hawaii, where the air contamination generally consists of gases continually erupting from the Kilauea volcano. Sulfur dioxide, carbon dioxide, hydrogen sulfide, hydrogen chloride, hydrogen fluoride, and sulfuric acid are the major airborne pollutants in Volcanoes National Park (e.g., intermittently registering up to 5 ppm SO2 in the atmosphere, with lower concentrations of other air contaminants). The example fuel cell bus will be powered by a large (e.g., 30 KW) fuel cell which will be powered by hydrogen stored on the bus and oxygen obtained from the atmosphere. If the contaminants in the atmosphere are allowed to enter the fuel cell (particularly the membrane electrode assembly, or “MEA”), then the catalyst will be poisoned, thus preventing the fuel cell from operating. Therefore, due to the harsh environmental conditions fuel cells may be exposed to, the air contaminants must be removed for proper fuel cell operation, and for extended fuel cell lifetime.
Current air purifying technologies use a carbon-based filter with a fixed lifetime, where air filters are merely replaced after a set period of time (e.g., scheduled intervals). However, there is currently no way of knowing when the filter lifetime is complete, which means the filters are either underutilized, wasting resources (filter materials, money, etc.), or over-utilized, potentially allowing dangerous contaminants to enter the fuel cell, thus causing reduced fuel cell power, or even permanent damage to the fuel cell.